String Equals. Use the equals () method to check if 2 strings are the same. The equals () method is case-sensitive, meaning that the string "HELLO" is considered to be different from the string "hello". The == operator does not work reliably with strings. Use == to compare primitive values such as int and char. The example code in this article was built and run using: Java 1.8.231 (1.8.x will do fine) Eclipse IDE for Enterprise Java Developers- Photon. 3. Difference between != and !a.equals (b). The main difference between == and equals is that “==” is used to compare primitives while equals () method is recommended to check equality of objects 4 days ago · Sometimes, we don’t have the ability to override the equals() method in a class. Nevertheless, we’d still like to compare one object against another to check whether they are the same. In this tutorial, we’ll learn a few ways for testing the equality of two objects without using the equals() method. 2. Example Classes We will be using two methods: Arrays.sort () and Arrays.equals () from the java.util package to solve this problem. The Arrays.sort () method sorts the elements of the array in increasing order. This method will accept the array which needs to be sorted and return the sorted array. The Arrays.equals () method checks the equality of the two equals() is a method of all Java Objects. But char is not an Object type in Java, it is a primitive type, it does not have any method or properties, so to check equality they can just use the == equals operator. 4 days ago · Comparing Doubles in Plain Java. The recommended algorithm to compare double values in plain Java is a threshold comparison method. In this case, we need to check whether the difference between both numbers is within the specified tolerance, commonly called epsilon: double epsilon = 0.000001d ; assertThat (Math.abs (d1 - d2) < epsilon).isTrue (); Naïve programmers often confuse the intent of the == operation with that of the Object.equals() method. This confusion is frequently evident in the context of processing String objects. As a general rule, use the Object.equals() method to check whether two objects have equivalent contents and use the equality operators == and != to test Also, you will need to override the hashCode method in your class Fraction in order to use HashMap. Since this equals implementation only depend on one value (the result of the fraction) you could use the following : public int hashCode () { return 0;//all Fraction return the same hashCode, which make HashMap call equals each time //EDIT: the Here is the excerpt from the java.lang.Object's equals() Javadoc. Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes. Consistent: a.equals(b) should always have the same value for unmodified objects. Null handling: a.equals(null) should be false. Hash code: Equal objects must have the same hash code. If we provide our own equals method, we also need to override hashCode. Since Java 7, the class java.util.Objects provides helpers for simplifying our code: umaviiw.